of Pleistophora periplanetae, Lutz and Splendore. 207 



polar capsule in the fresh state, the parasite belongs to the sub- 

 order Cryptocystes of the Myxosporidia and family Glugeidae, 

 which possess the characters of the sub-order. It belongs to the 

 sub-order Cryptocystes Myxosporidia and family Glugeidae, which 

 possesses the characters of the sub-order. It belongs to the 

 section Oligosporogenea (Doflein), because the trophozoite pro- 

 duces a single pansporoblast, and the production of numerous 

 spores by the pansporoblast relegates it to the genus Pleistophora. 

 It is this formation by the trophozoite of a single pansporoblast, 

 which removes the parasite from the genus Nosema, section Poly- 

 sporogonea, to the genus Pleistophora, section Oligosporogenea. 

 To sum up, the classification of the parasite is as follows : — 



Class. Sporozoa. 



Sub-class. Neosporidia. 



Order. Myxosporidia. 



Sub-order. Cryptocystes. 



Family. Glugeidae. 



Section. Oligosporogenea. 



Genus. Pleistophora. 



Species. Periplanetae. 

 There are several points of interest offered by the above scat- 

 tered details of the life-history of Pleistophora periplanetae, both 

 with respect to the Sporozoa in general and the Myxosporidia in 

 particular. In the first place it is seen that there are two very 

 definite phases, a trophic phase characterised by almost excessive 

 multiplication with a view to auto-infection, and a propagative 

 phase, characterised by a cessation of trophic activity and the 

 formation of resting spores. In this sharp division of the life 

 cycle into schizogonous and sporogonous phases Pleistophora peri- 

 planetae resembles Thelohania miilleri described by Stempell. 

 The occurrence of sporulation at the end of the trophic phase is 

 a feature which by no means agrees with Schaudinn's division of 

 the Sporozoa into Telosporidia, i.e. Sporozoa in which spore forma- 

 tion occurs at the end of the trophic phase, and Neosporidia, 

 which includes the Myxosporidia, in which spore formation occurs 

 during the trophic phase. As far as the point in the life-history, 

 at which spore formation occurs, is concerned, Pleistophora peri- 

 planetae is in exactly the same position as a Haemosporidian 

 or a Coccidian. In each case a trophic phase characterised by 

 vigorous multiplication is succeeded by a resting phase character- 

 ised by the production of resting spores. As Stempell remarks, 

 Schaudinn's grouping of the Myxosporidia and the Sarcosporidia 

 together in a sub-class separate from the rest of the Sporozoa is 

 probably well grounded, but the difference between the two sub- 

 classes must be expressed in other terms than the period of the 

 life-history at which sporulation occurs. Another point of interest 



